What additional laboratory finding is expected in a 4-year-old boy with suspected acute lymphoblastic leukemia?

The expected laboratory finding in a 4-year-old boy with suspected acute lymphoblastic leukemia (ALL) is the presence of the D10 antigen, also known as CD10. CD10 is a cell surface antigen that is commonly found on the blasts of lymphoblastic leukemia, distinguishing it from other hematologic malignancies. The presence of CD10 is an essential marker for identifying B-cell lineage in ALL, which is critical for diagnosis and determining the appropriate treatment approach.

In patients with acute lymphoblastic leukemia, the blasts typically demonstrate specific immunophenotypic characteristics, and CD10 expression is a key factor that supports the diagnosis. The detection of CD10 can be performed through flow cytometry or immunohistochemistry, providing vital information about the nature of the hematologic disorder.

The other findings listed are not associated with acute lymphoblastic leukemia. Auer rods are indicative of acute myeloid leukemia, Reed-Sternberg cells are characteristic of Hodgkin lymphoma, and smudge cells are often seen in chronic lymphocytic leukemia. Thus, focusing on the presence of CD10 antigen aligns with the recognized immunological profile of leukemia blasts in cases of acute lymphoblastic leukemia.